Animals Could Have Been Around Hundreds of Millions of Years Earlier Than Previously Believed
According to the most widely accepted theories, evolutionary biologists assert that life on Earth began roughly 4 billion years ago, beginning with single-celled bacteria and gradually giving way to more complex organisms. According to this same evolutionary timetable, the first complex organisms emerged during the Neoproterozoic era (ca. 800 million years ago), which took the form of fungi, algae, cyanobacteria, and sponges.
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